This invention relates to a fluid metering and flow dividing valve and, more specifically, to such a valve particularly adapted for use in a combustor associated with a gas turbine engine.
In the design of main combustion systems for gas turbine engines, uniform distribution of fuel to each of the combustor burners, which may number as many as 20 burners, is of major importance. It is common practice to position the combustor burners circumferentially about the periphery of the combustor even though variations in fluid flow may result from the different fluid heads associated with the differences in relative height of the burners with respect to each other. Numerous attempts have been made to overcome the variations in flow resulting from differences in fluid head. Recently fluidic valves have been utilized in close proximity to each burner to regulate the delivery of fuel from a common fuel manifold to the burners in a manner to insure that fuel flow is uniformly distributed to all burners.
The aforementioned fluidic valves may generally be comprised of vortex valves in which a control stream of fluid and a supply stream of fluid are each introduced into a common chamber in such a manner that the control stream modifies the flow characteristics of the supply stream. The control stream is utilized to introduce flow impedance in accordance with the flow requirements of the burner. Generally at low fuel flow requirements the impedance introduced by the control stream is high whereas at high fuel flow requirements the impedance introduced is low.
Delivery of both control and supply streams to the vortex valve at specific predetermined pressures and flow rates throughout the range of operating requirements of the combustor is accomplished by the provision of metering and flow dividing valves placed upstream of the vortex valves. Such valves regulate the supply and control streams of fuel in accordance with appropriate input signals and deliver the regulated streams to the vortex valves to effect delivery of the required fuel to the combustor burners. It is of major importance that the metering and flow dividing portions of the fluid distribution system be capable of operating without incurring damage from contaminantes occasionally found in the fuel. For instance, spool-type valves, well known in the art, which require close diametral clearances are susceptible to binding, side-loading and galling, all caused by fuel contamination, and hence spool-type valves have been found to be less than ideal for this application. Additionally, the metering and flow dividing portions of the fuel distribution should be limited to a short fluid flow path to reduce pressure losses in the fuel distribution system and should be compact, lightweight and comprised of a minimum of moving parts. It is also desirable that the metering and flow dividing valve elements be capable of purging any contaminates which may enter the valve with the fuel.